The present invention relate to a recovery unit for maintaining and recovering the ink ejection performance of a recording means which records images by ejection ink onto recording medium. It also relates to an ink jet recording apparatus which employs such a recovery unit.
An ink jet recording apparatus which records images by ejecting ink onto recording medium such as paper, fabric, plastic sheet, OHP sheet, and the like, in accordance with image data (recording data), has been widely used as an ordinary printer, a recording apparatus for a copying machine, facsimile machine, or the like, an output device for a complex electronic device such as a computer, a word processor, or the like, or an output device for a work station. Thus, there are various demands concerning the material for the recording medium used with an ink jet recording apparatus. In recent year, many researches have been made to meet such demands, and as a result, a recording apparatus capable of recording on fabric, leather, nonwoven fabric, in addition to paper (inclusive of thin paper and treated paper), which is the most commonly used recording medium, and thin plate of resin (OHP sheet or the like), has been developed, and has been put to practical use. Further, even a recording apparatus capable of using metal or the like as recording medium has been put to practical use.
An ink jet recording apparatus is low in operational noise, low in operational cost, easy to reduce in size, and easy to colorize. Therefore, it is widely used in the field of a printer, a copying machine, a facsimile, and the like. The recording means (ink jet recording head) of an ink jet recording apparatus has an ejection orifice (normally, in plurality) for ejecting an ink droplet, which is in the front surface of the recording means. The diameter of an ejection orifice has been in a range of several tens of microns. Recently, however, an ejection orifice has been further reduce in size to meet increased demand for improvement in image quality. In operation, an image (inclusive of letter and codes) is recorded on recording medium by ink droplets ejected from a plurality of ejection orifices in response to ejection signals created by processing, in a recording apparatus, the recording data sent from a host device.
In the above described ink jet recording apparatus which record images by ejecting ink from its recording means onto recording medium, ink is ejected from a plurality of microscopic ink ejection orifices, some of which sometimes become plugged, which results in poor ejection (inclusive of complete ejection failure), producing images of inferior quality. As for a countermeasure to this problem, it is a common practice to use a recovery unit for maintain and/or recovering the ink ejection performance of the recording means. Generally, a recovering unit comprises: a capping means for capping the ejection orifices of a recording head; a suctioning means connected to the capping means; and a wiping means for wiping away the foreign substances, for example, waste ink, on the recording head surface with the ejection orifices. In an operation for maintaining and/recovering the ink ejection performance of the recording head, the pump of the suctioning means is activated to generate negative pressure within the capping means to suction out the foreign substances such as ink with increased viscosity, air bubbles, and the like, from the ejection orifices, so that the ink within the ejection orifices are replaced with a fresh supply of ink.
In other words, an ink jet recording apparatus is provided with a recovering means, which is equipped with a recovery pump for keeping the recording head of the ink recording apparatus in the normal state of ejection, or for restoring the recording head to the normal state of ejection when the ejection orifices sometimes become plugged. In a recovery operation, ink is suctioned out of the ejection orifices by the negative pressure generated by the pump. As one of the recovery pumps, there is a tube type pump which generates negative pressure with the use of the volumetric change of the internal space of an elastic tube. More specifically, a tube type pump comprises a tube connected to the capping means which covers the recording head, and a roller which is kept pressed upon the tube by a force large enough to temporarily flatten the tube. In operation, the roller is rolled on the tube in a manner to temporarily flatten the tube, so that negative pressure is generated within the tube to suction the ink within the recording head, and that the ink which has been suctioned out of the recording head during the preceding temporary flattening of the tube by the roller, is discharged out of the tube.
A tube type pump is advantageous in that it is simple in structure, and therefore, can be reduced in size without incurring high cost. Thus, there have been developed various tube type pumps. Among them, there is a tube type pump which is very simple in a structure for flattening the tube or allowing the tube to recover; when a roller holding means is rotated in one direction, the roller is rolled on the tube in one direction, flattening the tube, and when the roller holding means is rotated in the opposite direction, the roller is moved in a manner to stop pressing the tube, allowing the tube to recover. One example of such a tube type pump is disclosed in Japanese Laid-open U.M. Application 53-106802. A tube type pump structured as disclosed in this application has a problem that as the force which keeps the roller pressed upon the tube is removed, the roller is made to spring, by the resiliency of the elastic tube, making collisional noises as it collides with the roller holding member. As a countermeasure to such a problem, Japanese Laid-open patent Application 200-012745 discloses an invention, according to which a rubber damper is disposed in alignment with where the roller is freed of the force applied thereto to flattened the tube, so that the collisional noises are reduced.
In a tube type pump structured as described above, however, even though the noises which occur as the roller is freed of the above described force, are reduced with the provision of a rubber damper, the noises similar to those caused by the collision between the roller and roller holding.member occur as the roller is sprung by the resiliency of the rubber damper when the roller passes through the damper. In order to prevent this problem, another rubber damper must be placed in alignment with where the roller comes through the first rubber damper, which will causes the similar noises as it let the roller pass. Therefore, third rubber damper must be disposed, and so on. In other words, it is necessary for a plurality of rubber dampers to be consecutively disposed to cover the entire range between where the roller becomes separated from the tube and where the roller begins to press the tube next time. Consequently, not only does component count increase, but also it becomes difficult to assemble a tube type pump, which results in cost increase.
The primary object of the present invention is to eliminate the collisional noises caused by the rollers, without relying on rubber dampers, in order to provide a quiet recovery unit which is simple in structure, and also an ink jet recording apparatus compatible with such a recovery unit.
According to an aspect of the present invention, there is provided a recoverying unit for maintenance and recovery of ink ejection performance of ink ejecting means, comprising: an elastic tube; a guide member for supporting said tube; a roller for pressing said tube; and a roller holding member, wherein said roller holding member is provided with a guide groove which connects a first position in which said roller presses said tube for substantially hermetically closing said tube, a second position in which said roller presses said tube with a greater pressing degree, and a third position in which said tube is opened, said guide groove is effective to guide movement of said roller between the first position and the third position.
According to another aspect of the present invention, there is provided an ink jet recording apparatus including a recoverying unit for maintenance and recovery of ink ejection performance of ink ejecting means, comprising: the recoverying unit including an elastic tube; a guide member for supporting the tube; a roller for pressing the tube; and a roller holding member, wherein the roller holding member is provided with a guide groove which connects a first position in which said roller presses said tube for substantially hermetically closing said tube, a second position in which said roller presses said tube with a greater pressing degree, and a third position in which said tube is opened, said guide groove is effective to guide movement of said roller between the first position and the third position.
According to the present invention, no noise is produced by abutment of the roller, and therefore, there is provided a recovery unit or an ink jet recording apparatus in which no noise is produced by movement of the roller without usign a rubber damper.
According to a further aspect of the present invention, drive transmitting means for rotating said roller holding member may be provided with a predetermined degree of angular play.
According to this aspect of the present invention, an additional operation such as shifting the recording means when capping it, is not required.
According to a further aspect of the present invention, it may be that said roller holding member includes a roller holder for holding said roller, a rotatable member for swingably holding the roller holder, and a spring for urging said roller holder, wherein said guide groove is formed on said roller holder and connects the first position and the third position such that radius of curvature of the roller is changed.
According to this aspect, the above-described object is more efficiently accomplished.